A few more usage-message tweaks

Minor stuff, but it corrects some errors in usage messages.

Signed-off-by: Ed Santiago <santiago@redhat.com>

cmd/podman/container.go

@@ -21,6 +21,7 @@ var (
 	listSubCommand  cliconfig.PsValues
 	_listSubCommand = &cobra.Command{
 		Use:     strings.Replace(_psCommand.Use, "ps", "list", 1),
+		Args:    noSubArgs,
 		Short:   _psCommand.Short,
 		Long:    _psCommand.Long,
 		Aliases: []string{"ls"},

cmd/podman/pod_start.go

@@ -18,7 +18,7 @@ var (
    Starts one or more pods.  The pod name or ID can be used.
 `
 	_podStartCommand = &cobra.Command{
-		Use:   "start POD [POD...]",
+		Use:   "start [flags] POD [POD...]",
 		Short: "Start one or more pods",
 		Long:  podStartDescription,
 		RunE: func(cmd *cobra.Command, args []string) error {

cmd/podman/system_prune.go

@@ -23,6 +23,7 @@ var (
 `
 	_pruneSystemCommand = &cobra.Command{
 		Use:   "prune",
+		Args:  noSubArgs,
 		Short: "Remove unused data",
 		Long:  pruneSystemDescription,
 		RunE: func(cmd *cobra.Command, args []string) error {